Question: Simplify the following expression: $k = \dfrac{3t}{4} - \dfrac{6t}{5}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $4$ and $5$ $\lcm(4, 5) = 20$ $ k = \dfrac{5}{5} \cdot \dfrac{3t}{4} - \dfrac{4}{4} \cdot \dfrac{6t}{5} $ $k = \dfrac{15t}{20} - \dfrac{24t}{20}$ $k = \dfrac{15t -24t}{20}$ $k = \dfrac{-9t}{20}$